The present invention relates to a continuously-variable-ratio belt drive assembly.
The present invention may be used to advantage, though not exclusively, on internal combustion engine motor vehicles, particularly low-power types such as micro- or so-called utility vehicles.
In such vehicles, the velocity ratio between the engine and the wheels must be varied to adapt the output power of the engine to operating characteristics such as desired vehicle speed, vehicle load, etc.
Consequently, such vehicles traditionally feature, between the engine and the wheels, a drive comprising a variable-speed belt drive and possibly also a centrifugal clutch device fitted between the input member and the intermediate shaft, and wherein the two shafts are engaged by greatly increasing engine speed, and the velocity ratio is varied as a function of ultimate engine speed.
Known assemblies of this sort have the drawback of being fairly rigid in terms of both engagement and velocity ratio variation, and of normally requiring a high engine speed to fully engage the clutch device, thus dissipating a considerable amount of energy. Moreover, engagement is invariably rough, thus resulting in discomfort to the user.
It is an object of the present invention to eliminate the aforementioned drawbacks by providing a continuously-variable-ratio belt drive assembly wherein engagement of the clutch device is smooth and not necessarily produced by increasing engine speed, and wherein the velocity ratio in use is determined, not rigidly by the speed of the engine, but by an external control.
It is a further object of the invention to provide a drive assembly having the above characteristics, and which is also designed to afford substantial advantages in terms of maintenance and operation of the assembly itself.
These and other objects are achieved by the present invention as characterized in the accompanying claims.